CVE-2018-20859 in edx-platform
Summary
by MITRE
edx-platform before 2018-07-18 allows XSS via a response to a Chemical Equation advanced problem.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2018-20859 represents a cross-site scripting weakness within the edx-platform learning management system that was prevalent prior to the 2018-07-18 release. This flaw specifically affects the handling of responses within Chemical Equation advanced problem types, which are commonly used in chemistry educational assessments. The vulnerability stems from insufficient input validation and output sanitization mechanisms that fail to properly escape or filter user-provided content before rendering it within web pages. When students submit responses to chemical equation problems, the platform processes these inputs without adequate protection against malicious script injection attempts, creating an avenue for attackers to execute arbitrary JavaScript code in the context of other users' browsers.
The technical exploitation of this vulnerability occurs through the manipulation of input fields within the Chemical Equation problem type, where attackers can craft malicious responses containing script tags or other XSS payloads. These payloads are then executed when other users view the problematic content, potentially leading to session hijacking, credential theft, or redirection to malicious sites. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws in web applications, and demonstrates how insufficient sanitization of user-controllable data can create persistent security risks. The attack surface is particularly concerning within educational platforms where multiple users interact with shared content, as a single compromised response can affect all users who encounter that content.
The operational impact of CVE-2018-20859 extends beyond simple script execution, as it can enable attackers to escalate privileges and access sensitive user data within the platform. In educational environments, this vulnerability could allow malicious actors to steal student information, access instructor credentials, or manipulate assessment results. The risk is compounded by the fact that the vulnerability affects the core functionality of the platform's assessment system, potentially undermining the integrity of academic evaluations. From an ATT&CK framework perspective, this vulnerability maps to T1059.007 for scripting languages and T1531 for credential access, as attackers can leverage the XSS to harvest session cookies and credentials from authenticated users.
Organizations utilizing edx-platform should implement immediate mitigations including input validation and output encoding for all user-provided content within advanced problem types, particularly those involving chemical equations or mathematical expressions. The platform should employ Content Security Policy headers to prevent execution of unauthorized scripts, and implement proper sanitization of all user inputs before rendering them in web contexts. Regular security audits and input validation testing should be conducted to identify similar vulnerabilities across other problem types. Additionally, administrators should consider implementing web application firewalls to detect and block suspicious input patterns, while ensuring all users are promptly updated to the patched version released on 2018-07-18 that addresses this specific vulnerability through enhanced input sanitization mechanisms.